Production of the 57 kDa major surface antigen by a non-agglutinating strain of the fish pathogen Renibacterium salmoninarum

Both the prevalence and tissue titer of viral hemorrhagic septicemia virus (VHSV) increased in Pacific herring Clupea pallasi following their introduction into net pens (pounds) used in the closed pound spawn-on-kelp (SOK) fishery in Prince William Sound, Alaska. VHSV was also found in water samples from inside and outside the SOK pounds after herring had been confined for several days; however, water samples taken near wild free-ranging, spawning herring either failed to test positive or tested weakly positive for virus. Little or no virus was found in tissue samples from free-ranging, spawning herring captured from the vicinity of the pounds, nor did the prevalence of VHSV increase following spawning as it did in impounded herring. The data indicated that increased prevalences of VHSV were correlated with confinement of herring for the closed pound SOK fishery and that infection was spread within the pounds through waterborne exposure to virus particles originating from impounded fish. In addition, pounds containing predominantly young fish had higher prevalences of VHSV, suggesting that older fish may be partially immune, perhaps as a result of previous infection with the virus. Operation of SOK pounds during spawning seasons in which young herring predominate may amplify the disease and possibly exacerbate the population fluctuations observed in wild herring stocks.     

Discrimination of Baltic herring populations with respect to Anisakis simplex larvae infection

Samples of herring Clupea harengus in the Baltic were collected during the spawning season in western, middle and eastern waters off the Polish coast. Two samples were taken per area, several morphometric characters were measured and some meristic characters (vertebrae and gill rakers) were counted. Infection with Anisakis simplex larvae, total length, age and maturity stage were recorded. Univariate and multivariate statistical tests were used to compare the samples, discriminant analysis was applied to separate herring populations and the fraction of herring populations in each area was estimated. The results obtained indicated that infected fish represented a mixed group of western and central Baltic herring. In the first samples collected from each area, the share of the western population decreased from 40% in the western to 18% in the middle and 13% in the eastern coasts. The share of western herring was higher in the second samples collected in the same area and decreased from 91% in the western coast to 14 and 32% in the middle and eastern ones, respectively.     

Biological features of the common fish species in Olyutorsky-Navarin region and the adjacent waters of the Bering Sea: 2. Families Macrouridae,Clupeidae, and Osmeridae

Biological features of the four common fish species, giant grenadier Albatrossia pectoralis (Macrouridae), Pacific herring Clupea pallasii (Clupeidae), Pacific rainbow smelt Osmerus mordax dentex, and Pacific capelin Mallotus villosus catervarius (Osmeridae), were studied under the 20-year dataset (1995?2015). These species inhabit the northwestern Bering Sea in the summer–autumn period and form the schoolings in the Olyutorsky-Navarin region. The size–age parameters of the fish caught by different sampling gear, as well as the peculiarities of the body length and body weight dynamics, spawning periods, spawning range, and conditions, were analyzed. The largest specimens of giant grenadier, Pacific herring, and Pacific rainbow smelt were observed in the catches performed by the bottom setline and the gill nets; the smallest fish were found in the trawl catches. The body length and body weight of Pacific herring were larger in the pelagic trawls compared to the bottom trawls; an opposite pattern was observed for the Pacific capelin. The abundant year-class in the species with short life cycle (capelin and herring) is well tracked on the longterm plots of the fish body size; this is accompanied by the decrease of their biological parameters. Herring stock covers large growing grounds; smaller body size was observed for the herring grazing in the coastal waters; young specimens dominate here.     

Adult body growth and reproductive investment vary markedly within and across Atlantic and Pacific herring: a meta-analysis and review of 26 stocks

Reviews in Fish Biology and Fisheries - Life-history traits of Pacific (Clupea pallasii) and Atlantic (Clupea harengus) herring, comprising both local and oceanic stocks subdivided into...     

Diel differences in fish assemblages in nearshore eelgrass and kelp habitats in Prince William Sound,Alaska

The importance of a particular habitat to nearshore fishes can be best assessed by both diurnal and nocturnal sampling. To determine diel differences in fish assemblages in nearshore eelgrass and understory kelp habitats, fishes were sampled diurnally and nocturnally at six locations in western Prince William Sound, Alaska, in summer 2007. Abundance of fish between day and night were similar, but species composition and mean size of some fish changed. Species richness and species diversity were similar in eelgrass during the day and night, whereas in kelp, species richness and species diversity were greater at night than during the day. In eelgrass, saffron cod (Eleginus gracilis) was the most abundant species during the day and night. In kelp, the most abundant species were Pacific herring (Clupea pallasii) during the day and saffron cod at night. Diel differences in fish size varied by species and habitat. Mean length of saffron cod was similar between day and night in eelgrass but was greatest during the day in kelp. Pacific herring were larger at night than during the day in kelp. Diel sampling is important to identity nearshore habitats essential to fish and help manage fish stocks at risk.     

Introgressive hybridization between the Atlantic and Pacific herring (<Emphasis Type="Italic">Clupea harengus</Emphasis> and <Emphasis Type="Italic">Clupea pallasii</Emphasis>) in the White Sea,Barents and Kara Seas evidenced by microsatellites

In the North of Europe two sister species of herring—the Atlantic Clupea harengus and Pacific Clupea pallasii have post-glacially come into secondary contact. Although the breeding areas of the two species are thought to be separate, previous genetic studies based on allozyme and mitochondrial DNA data have supported the existence of introgression from the Atlantic herring to the Pacific herring. In this study, we employed microsatellite markers to explore the extent of introgressive hybridization between these fishes. Bayesian methods for assigning individuals to populations and identifying admixture proportions were applied to the genetic data based on ten microsatellites. Results indicated that 18 out of 464 Pacific herring (3.88%) were likely admixed. Some of the hybrid individuals contained genotypes suggesting that introgressive hybridization is an ongoing process. Despite some admixture, the Atlantic and Pacific herring gene pools remain sharply distinct (the average proportions of membership to “Atlantic” and “Pacific” clusters were Q_A = 0.998 and Q_P = 0.974, respectively), suggesting that hybridization was not frequent. The discovery of introgression among herring species opens new questions about the mechanisms underlying the observed pattern of genetic population differentiation in the North European Pacific herring.     

Larval distribution, abundance, and stock structure of British Columbia herring

Pacific herring Clupea pallasi spawn in shallow and intertidal areas. Larval distributions and abundance of three major and several minor stocks were examined to determine if larvae mix among different spawning locations. The surveys were short, intensive, and occurred mainly within the first 30 days of larval life. Each major stock had a discrete larval distribution with continuous larval distributions within stock boundaries. Some overlap of distributions occurred among smaller stocks. Most larvae were found in inshore waters but there were no obvious oceanographic factors, such as fronts or eddies, to explain all the distributions. Estuarine circulation in inlets could promote larval retention in some areas. The results support the present geographic definitions for local herring stocks. The results are generally consistent with the concept of discrete larval distribution, including retention areas, as the basis for herring Stock Structure.     

Evidence for Two Highly Differentiated Herring Groups at Goose Bank in the Barents Sea and the Genetic Relationship to Pacific Herring, Clupea pallasi

Genetic studies on Atlantic herring, Clupea harengus, have generally revealed a low level of genetic variation over large geographic areas. Genetically distinct herring populations in some of the Norwegian fjords are exceptions, and juvenile herring from the large oceanic herring, Norwegian Spring Spawners (NSS), are often found in mixture with local fjord populations as well as widely distributed in the Barents Sea. Research surveys in the eastern Barents Sea (Goose Bank) in 1993, 1994 and 2001 included collection of herring samples for allozyme analyses. As expected the results identified juveniles from NSS stock, but an additional unique group of herring (low vertebrae number), being almost fixed for alternative alleles at several allozyme loci, was detected. In some cases, the two groups of herring were taken in the same trawl catches as documented by highly significant departure from Hardy—Weinberg expectation with large excess of homozygotes providing evidence for population mixing. Large genetic differences (Nei's genetic distance = 1.53; F_ST = 0.754) were detected in pairwise comparisons based on five allozyme loci. The two herring groups were also compared with reference samples of Pacific herring, Clupea pallasi, including one sample from Japan Sea and three Alaskan samples. UPGMA dendrogram based on five allozyme loci revealed a close genetic relationship between the low vertebrae herring in the Barents Sea and the group of samples of Pacific herring. Although significant different in allele frequencies, one of the herring samples clustered together with the reference sample from Bering Sea with genetic distance of 0.008 and F_ST value of 0.032. The close genetic relationship found in this paper, suggest a re-evaluation of the taxonomic status of the Barents Sea herring populations investigated.     

Spatial and Temporal Variability in Juvenile Pacific Herring, Clupea pallasi, Growth in Prince William Sound, Alaska

We examined the spatial and temporal variability of juvenile Pacific herring, Clupea pallasi, growth within Prince William Sound, Alaska. Pacific herring, ranging from post-larval to mature fish, were collected from four spatially segregated bays between October 1995 and March 1998. Linear growth equations from each bay were similar. However, growth rates and wet weight-at-length, reflecting condition, of juvenile Pacific herring cohorts varied seasonally and annually. The short term spatial variability in juvenile Pacific herring growth suggested that each bay was a unique nursery area. The physical and biological conditions within each bay appeared to dictate Pacific herring growth rate.     

A morphometric investigation of the small yellow croaker (Larimichthys polyactis Bleeker, 1877): evidence for subpopulations on the Chinese coast

In this study the morphometric characteristics based on the truss network system were constructed from the body shapes and used to investigate the population structure of the small yellow croaker (Larimichthys polyactis Bleeker, 1877). From April to June 2013, a total of 431 fish samples were collected from commercial catches acquired with bottom trawlers (20 × 20 mm) in seven main spawning grounds along the coast of China. The results of principal component and discriminant function analyses indicated a clear distinction among the regional stocks and within the Haizhou Bay (HZB) stock. Observed differences primarily involved head measurements, body length and tail size, which were associated with environmental factors. Latitudinal gradient of the stock distribution and the relationship among the stocks provided further evidence for the existence of subpopulations and the re‐division of the East China Sea group. Moreover, the temporal inter‐structure of the HZB stock is a potential reason for the contrast in results from previous studies. Additional thorough studies of migration trajectories are required for a conclusive and improved understanding of the population structure.     

How relative size and abundance structures the relationship between size and individual growth in an ontogenetically piscivorous fish

While individual growth ultimately reflects the quality and quantity of food resources, intra and interspecific interactions for these resources, as well as individual size, may have dramatic impacts on growth opportunity. Out‐migrating anadromous salmonids make rapid transitions between habitat types resulting in large pulses of individuals into a given location over a short period, which may have significant impact on demand for local resources. We evaluated the spatial and temporal variation in IGF‐1 concentrations (a proxy for growth rate) and the relationship between size and concentration for juvenile Chinook salmon in Puget Sound, WA, USA, as a function of the relative size and abundance of both Chinook salmon and Pacific herring, a species which commonly co‐occurs with salmonids in nearshore marine habitats. The abundance of Chinook salmon and Pacific herring varied substantially among the sub‐basins as function of outmigration timing and spawn timing, respectively, while size varied systematically and consistently for both species. Mean IGF‐1 concentrations were different among sub‐basins, although patterns were not consistent through time. In general, size was positively correlated with IGF‐1 concentration, although the slope of the relationship was considerably higher where Pacific herring were more abundant than Chinook salmon; specifically where smaller individual herring, relative to Chinook salmon, were more abundant. Where Pacific herring were less abundant than Chinook salmon, IGF‐1 concentrations among small and large Chinook salmon were more variable and showed no consistent increase for larger individuals. The noticeable positive effect of relative Pacific herring abundance on the relationship between size and individual growth rates likely represents a shift to predation based on increased IGF‐1 concentrations for individual Chinook salmon that are large enough to incorporate fish into their diet and co‐occur with the highest abundances of Pacific herring.     

Dietary variation within and between populations of northeast Atlantic killer whales,Orcinus orca,inferred from δ13C and δ15N analyses

Epidermal skin samples from eastern North Atlantic killer whales, Orcinus orca, were analyzed for carbon and nitrogen stable isotope ratios. From those, comparisons within a data set of 17 samples collected from Tysfjord, Norway, in November suggested that diet is relatively specialized during this time period at this location. There were significant differences between a small set of samples from Iceland and those collected from Norway, which had all been assigned to the same population by a previous population genetics study. The results would be consistent with matrilines feeding on either the Norwegian or Icelandic stocks of Atlantic herring (Clupea harengus). There was no significant difference within Icelandic samples between those assigned to the population known to feed upon herring and those assigned to a population hypothesized to follow Atlantic mackerel (Scomber scombrus). The greatest differences were between the epidermal samples analyzed in this study and tooth and bone collagen samples from the North Sea that were analyzed previously, which also showed significantly more variation in isotopic ratios than found for skin samples. These differences could reflect differences in turnover rate, differences in diet‐tissue fractionation and discrimination due to the amino acid composition of the different tissues, and/or greater competition promoting dietary variation between groups in the North Sea.     

Fisheries management in practice: review of 13 commercially important fish stocks

This paper comparatively reviews several commercially important fish stocks, their state and their management in various regions of the world including Japanese anchovy, Bay of Biscay anchovy, North Sea sandeel, North Sea herring, Icelandic cod, Barents Sea cod, South African cape hakes, sockeye salmon, chinook salmon, southern bluefin tuna, Pacific halibut, Greenland halibut and Patagonian toothfish. The reviewed fish stocks are systemized in three categories: (1) stock properties and status; (2) management structure and objectives; and (3) management advice. We gather evidence to outline qualities of management regimes that are recommended and highlight those that most often fail. Robust management, biological limits (reference points), implementation and consensus are critical points that separate successful and unsuccessful management regimes. We evaluate each fish stock’s management performance relative to its management objectives and current conservation issues. Furthermore, we point out the importance of stakeholder involvement in fisheries management as well as the problems that international fisheries commissions face through examples from the case studies. Management successes tended to be single-nation and single-stock fisheries with capacity control and clear stakeholder involvement. Fisheries with fleet overcapacity, unclear objectives and illegal activity characterized the case studies with management problems.     

Evidence of stable genetic structure across a remote island archipelago through self‐recruitment in a widely dispersed coral reef fish

We used microsatellite markers to assess the population genetic structure of the scribbled rabbitfish Siganus spinus in the western Pacific. This species is a culturally important food fish in the Mariana Archipelago and subject to high fishing pressure. Our primary hypothesis was to test whether the individuals resident in the southern Mariana Island chain were genetically distinct and hence should be managed as discrete stocks. In addition to spatial sampling of adults, newly‐settled individuals were sampled on Guam over four recruitment events to assess the temporal stability of the observed spatial patterns, and evidence of self‐recruitment. We found significant genetic structure in S. spinus across the western Pacific, with Bayesian analyses revealing three genetically distinct clusters: the southern Mariana Islands, east Micronesia, and the west Pacific; with the southern Mariana Islands being more strongly differentiated from the rest of the region. Analyses of temporal samples from Guam indicated the southern Mariana cluster was stable over time, with no genetic differentiation between adults versus recruits, or between samples collected across four separate recruitment events spanning 11 months. Subsequent assignment tests indicated seven recruits had self‐recruited from within the Southern Mariana Islands population. Our results confirm the relative isolation of the southern Mariana Islands population and highlight how local processes can act to isolate populations that, by virtue of their broad‐scale distribution, have been subject to traditionally high gene flows. Our results add to a growing consensus that self‐recruitment is a highly significant influence on the population dynamics of tropical reef fish.     

Phenological and distributional shifts in ichthyoplankton associated with recent warming in the northeast Pacific Ocean

Understanding changes in the migratory and reproductive phenology of fish stocks in relation to climate change is critical for accurate ecosystem‐based fisheries management. Relocation and changes in timing of reproduction can have dramatic effects upon the success of fish populations and throughout the food web. During anomalously warm conditions (1–4°C above normal) in the northeast Pacific Ocean during 2015–2016, we documented shifts in timing and spawning location of several pelagic fish stocks based on larval fish samples. Total larval concentrations in the northern California Current (NCC) during winter (January–March) 2015 and 2016 were the highest observed since annual collections first occurred in 1998, primarily due to increased abundances of Engraulis mordax (northern anchovy) and Sardinops sagax (Pacific sardine) larvae, which are normally summer spawning species in this region. Sardinops sagax and Merluccius productus (Pacific hake) exhibited an unprecedented early and northward spawning expansion during 2015–16. In addition, spawning duration was greatly increased for E. mordax, as the presence of larvae was observed throughout the majority of 2015–16, indicating prolonged and nearly continuous spawning of adults throughout the warm period. Larvae from all three of these species have never before been collected in the NCC as early in the year. In addition, other southern species were collected in the NCC during this period. This suggests that the spawning phenology and distribution of several ecologically and commercially important fish species dramatically and rapidly changed in response to the warming conditions occurring in 2014–2016, and could be an indication of future conditions under projected climate change. Changes in spawning timing and poleward migration of fish populations due to warmer ocean conditions or global climate change will negatively impact areas that were historically dependent on these fish, and change the food web structure of the areas that the fish move into with unforeseen consequences.     

Stock structure analysis of ‘Bombay duck’ (Harpadon nehereus Hamilton, 1822) along the Indian coast using truss network morphometrics

Harpadon nehereus, commonly known as ‘Bombay duck’, is a fish with a discontinuous distribution along the Indian peninsula. The fisheries are dominant on the north‐east and north‐west coast but are absent in commercial landings below 15° north latitude. Heretofore stock assessment studies had not considered the various spawning stock components that replenish this fishery, therefore the present study. Fish samples were collected from four locations: two each from the northeast and the northwest coasts. Twenty‐four morphometric variables were measured using a box‐truss network method. Factor analysis of these variables differentiated the east and the west coast fish populations. Multiple comparisons on the factor scores indicated two independent stocks on the east coast, whereas the fishery on the west coast is replenished by a single stock. The important morphometric traits that accounted for most of the stock variations were related to swimming adaptations of the fish. Future stock assessments can consider the population on the west coast as a single stock when formulating management plans. To harvest the resource in a sustainable manner, the maritime states on the west coast should adopt collaborative efforts towards managing this fishery.     

Isolation of the North American strain of viral hemorrhagic septicemia virus (VHSV) associated with epizootic mortality in two new host species of Alaskan marine fish

Thousands of dead Pacific herring Clupea pallasi, Pacific hake Merluccius productus and walleye pollock Theragra chalcogramma were reported in Lisianski Inlet near Pelican, Alaska, USA, on August 1, 1998. The Pacific hake and pollock continued to die through the end of September. Virological examinations of dead fish identified the North American strain of viral hemorrhagic septicemia virus (VHSV) from all 3 species of fish as well as associated high virus titers and possible histopathological lesions. No other primary fish pathogens were detected and there were no apparent environmental causes for fish mortality. This is the first report of VHSV in 2 new Alaskan fish host species and of a natural epizootic associated with VHSV in which progressive mass mortality was observed simultaneously in herring and 2 other species of free-ranging marine fish.     

Population structure and variability of Pacific herring (<Emphasis Type="Italic">Clupea pallasii</Emphasis>) in the White Sea,Barents and Kara Seas revealed by microsatellite DNA analyses

Pacific herring, Clupea pallasii, have recently colonised the northeast Atlantic and Arctic Oceans in the early Holocene. In a relatively short evolutionary time, the herring formed a community with a complex population structure. Previous genetic studies based on morphological, allozyme and mitochondrial DNA data have supported the existence of two herring subspecies from the White Sea and eastern Barents and Kara Seas (C. p. marisalbi and C. p. suworowi, respectively). However, the population structure of the White Sea herring has long been debated and remains controversial. The analyses of morphological and allozyme data have previously identified local spawning groups of herring in the White Sea, whereas mtDNA markers have not revealed any differentiation. We conducted one of the first studies of microsatellite variation for the purpose of investigating the genetic structure and relationship of Pacific herring among ten localities in the White Sea, the Barents Sea and the Kara Sea. Using classical genetic variance-based methods (hierarchical AMOVA, overall and pairwise F _ST comparisons), as well as the Bayesian clustering, we infer considerable genetic diversity and population structure in herring at ten microsatellite loci. Genetic differentiation was the most pronounced between the White Sea (C. p. marisalbi) versus the Barents and Kara seas (Chesha–Pechora herring, C. p. suworowi). While microsatellite variation in all C. pallasii was considerable, genetic diversity was significantly lower in C. p. suworowi, than in C. p. marisalbi. Also, tests of genetic differentiation were indicating significant differentiation within the White Sea herring between sympatric summer- and spring-spawning groups, in comparison with genetic homogeneity of the Chesha–Pechora herring.     

Genetic stock identification of overwintering chum salmon in the North Pacific Ocean

Understanding stock and age-specific seasonal migrations of Pacific salmon during ocean residence is essential to both the conservation and management of this important resource. Based upon 11 microsatellites assayed on 265 individuals collected aboard international research surveys during winter 2009, we found substantial differences in the age-specific origin of chum salmon (Oncorhynchus keta) in the North Pacific Ocean. Overall, Asian stocks dominated the collections, however, ocean age 1 fish were primarily of Japanese origin and ocean age 2–3+ fish were predominantly of Russian origin. These results suggest that cohorts of chum salmon stocks migrate nonrandomly in the North Pacific Ocean and adjacent seas.     

Production and characterization of monoclonal antibodies to IgM of Pacific herring (Clupea pallasii)

Pacific herring (Clupea pallasii) have a central role in the North Pacific ecosystem as a forage fish species and are natural reservoirs of several important finfish pathogens, including Viral hemorrhagic septicemia virus (VHSV). Here, we report the identification of the gene encoding the immunoglobulin mu (IgM) heavy chain, as well as the development and characterization of monoclonal antibodies (MAbs) that specifically react with Pacific herring IgM. Pacific herring immunoglobulin was purified and consisted of heavy and light chains of approximately 80 and 25?kDa. Three hybridoma clones were initially identified by ELISA as reactive with purified immunoglobulin but only one clone was able to detect an 80?kDa protein in Pacific and Atlantic herring (Clupea harengus) whole plasma by denaturing western blot. However, all three MAbs were able to precipitate an 80?kDa protein from Pacific herring and LCMS sequencing of peptide fragments derived from this protein matched the predicted amino acid sequence of the cloned, heavy chain gene. In addition, two of the MAbs stained cells within the putative lymphocyte gates for the spleen, anterior kidney and posterior kidney but were not reactive for myeloid/granulocyte gates, which is consistent with these MAbs reacting with surface IgM(+) B-cells. To our knowledge, this is the first report of IgM-related gene sequences and anti-IgM monoclonal antibodies from any member of the family Clupeidae. The antibodies produced in this study are critical for achieving our long-term goal of conducting serological surveillance to assess pathogen exposure in natural populations of Pacific herring.